Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$120.68	5.626%	$127.4695	$127.47	$127.45	$127.50
Purchase #2	$113.32	3.617%	$117.4188	$117.42	$117.40	$117.40
Purchase #3	$115.91	12.241%	$130.0985	$130.10	$130.10	$130.10
Purchase #4	$70.88	7.444%	$76.1563	$76.16	$76.15	$76.20
Purchase #5	$203.85	11.502%	$227.2968	$227.30	$227.30	$227.30
Purchase #6	$203.72	11.855%	$227.871	$227.87	$227.85	$227.90
Purchase #7	$99.87	10.156%	$110.0128	$110.01	$110.00	$110.00
7 purchase totals =	$928.23		$1,016.3237	$1,016.33	$1,016.25	$1,016.40